There are often other factors too, than just the direct fishing, that keep a population low.

In the west of North America, like most places, almost all of the old growth forest was logged.

Some places where the soil and subsoil was particularly vulnerable to erosion and landsliding or just didn't have a lot of water capacity in the first place like on dry mountains, after these trees were removed and most of the soil washed away from rain, the forest simply has not come back a hundred years later. There are little trees gradaually getting started, and lots of mostly bare soil or rock still where erosion from rain is able to outpace the vegetation growth. It will likely take many thousand years for trees to get to the size they were before, and to build up the capacity for holding water like it had been.

In more abundant forests, trees regrow faster. But even there, a hundred years later, the total biomass per acre is often 10% of what it was as old growth forest, and the capacity for holding water on the land similarly much reduced. The old growth forests were the result of nature doing its thing often with help from humans for thousands of years and continually becoming richer. Eventually a major disturbance sets it back, but this might only happen ever 5 or 10 thousand years. This time humans did it.

Example regarding clams: https://www.atlasobscura.com/articles/pearl-buttons-muscatin...

They never actually stopped fishing it though. It's regulated at a level to prevent 100% collapse, there was never political support to let it truly recover by banning fishing for a decade or two.